Rivendell ("cloven-dell") is the Common Speech translation of the Sindarin name Imladris ("deep dale of the cleft"). An alternative (or complementary) etymology, gives Rivendell as the Englished version of the Westron name Karningul (itself a translation of Imladris).
The name Imladris is also glossed as "Canyon of the Cleft" and "flat-floared valley of the Cleft".
Sindarin name of Rivendell (LotR/657), a combination of imlad “deep valley” and riss “cleft” (PE17/87), so literally “Deep Dale of the Cleft” (RC/482).
Conceptual Development: In Lord of the Rings drafts from the 1940s, this name first appeared as N. Imlad-ril (rejected) >> Imladrist (TI/120), but was soon revised to Imladris (TI/146), a form that also appeared in The Etymologies with essentially the same derivation as given above (Ety/RIS²).